First of all I know Voltage goes Up in Series and Capacity/Total Current in Parallel.
But I have confusions,
For example let’s say we have 2 Li-ion cells,
Both 3.7 volts and 2000 mAh or say 2 AH.
When their volts go up to 7.4 volts why doesn’t it go to 4000 mAh as well?
Where does the other 2000 mAh go?
I know because Battery is now delivering current at faster pressure (volts) but it still doesn’t explain why battery is not called 4000 mAh after It’s put in series.
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In: Physics
Milliamp hours are not a measure of energy, but rather, electrical charge – they tell you how long a cell can supply a given current not how much energy it stores. To get the latter (in mWh), you need to multiply by the voltage.
If a battery has a capacity of 2000mAH, that means it can deliver 2A of current for one hour or 1A for two hours. When you put two cells in series, the same current must flow through both of them. If you put two 2000mAH cells in series, and your circuit draws 1A of current, then 1A of current flows through both cells, and therefore, both cells will be drained after 2 hours.
But the voltages add, so with 2 3.7V cells you deliver 7.4V to your circuit. Therefore, the two cells in series are delivering twice as much power at the same current because the voltage is doubled. You have twice as much energy available, but you are draining it twice as fast. If instead you wire the batteries in parallel, then the opposite happens – now, the voltage is the same for both batteries, but the current is shared between them. If your circuit is drawing 1A, then with the cells wired in parallel, you would draw 0.5A from each cell, so they would last 4 hours.
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